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SLEEP(1) General Commands Manual SLEEP(1)

sleep
suspend execution for an interval of time

sleep seconds

The sleep utility suspends execution for a minimum of the specified number of seconds. This number must be positive and may contain a decimal fraction. sleep is commonly used to schedule the execution of other commands (see below).

 
 
Terminate normally, with a zero exit status.

The sleep utility exits 0 on success, and >0 if an error occurs.

Wait a half hour before running the script command_file (see also the at(1) utility):
(sleep 1800; sh command_file >& errors)&
To repetitively run a command (with csh(1)):
while (! -r zzz.rawdata) 
	sleep 300 
end 
foreach i (*.rawdata) 
	sleep 70 
	awk -f collapse_data $i >> results 
end
The scenario for such a script might be: a program currently running is taking longer than expected to process a series of files, and it would be nice to have another program start processing the files created by the first program as soon as it is finished (when zzz.rawdata is created). The script checks every five minutes for this file. When it is found, processing is done in several steps by sleeping 70 seconds between each awk(1) job.
To monitor the growth of a file without consuming too many resources:
while true; do 
	ls -l file 
	sleep 5 
done

at(1)

The sleep utility is compliant with the IEEE Std 1003.1-2008 (“POSIX.1”) specification.
The handling of fractional arguments is provided as an extension to that specification.

A sleep utility appeared in Version 4 AT&T UNIX.
August 16, 2016 OpenBSD-current